使用JQuery获取TD的值

我有一个非常简单的表，只有两行.
我在想从ID为"row2"的TD获取值的最佳方法是什么.

I got a very simple Table with only two rows.
I was thinking what is the best way to get the value from the TD with ID "row2".

<Table id="testing>
<tr>
<th>
</th>
<td id="row1">hello</td>
</tr>
<tr>
<th>
</th>
<td id="row2">world</td>
</tr>
</table>

这是我的尝试:

Here is my attempt:

$(document).ready(function(){ 
      var r=$("#testing":row2).val();
      alert(r);
});

但是我看不到任何消息弹出. 如果要同时指定Table ID和TD ID，该怎么办?

But I couldn't see any message pop up. What shall I do in the JQuery code if I want to specify the Table ID along with the TD ID?

 var r=$("#testing":row2).text();
 var r=$("#testing").children("row2").text();